The present invention relates to an ink-jet recording head, in which a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, a piezoelectric element is provided via this vibration plate, and ink droplets are ejected by displacement of the piezoelectric element. Furthermore, the present invention relates to an ink-jet recording apparatus.
With regard to the ink-jet recording head, in which a portion of a pressure generating chamber communicating with a nozzle orifice that ejects ink droplets is constituted of a vibration plate, this vibration plate is deformed by a piezoelectric element to pressurize ink in the pressure generating chamber, and ink droplets are ejected from the nozzle orifice, two types of recording heads are put into practical use. One is a recording head using a piezoelectric actuator of longitudinal vibration mode that expands and contracts in the axis direction of the piezoelectric element, and the other one uses a piezoelectric actuator of flexural vibration mode.
The former one can change the volume of the pressure generating chamber by abutting the end surface of the piezoelectric element against the vibration plate, and manufacturing of a head suitable to high density printing is enabled. On the contrary, a difficult process in which the piezoelectric element is cut and divided in a comb tooth shape to make it coincide with the array pitch of the nozzle orifice and a method so that the cut and divided piezoelectric element is aligned and fixed to the pressure generating chamber is necessary, thus there is a problem of a complex manufacturing process.
On the other hand, in the latter, the piezoelectric element can be fabricated and installed on a vibration plate by a relatively simple process in which a green sheet, which is piezoelectric material, is adhered while fitting the shape thereof to the pressure generating chamber shape and is sintered. However, a certain size of vibration plate is required due to the usage of flexural vibration, thus there is a problem that a high density array of the piezoelectric elements is difficult.
In order to solve such a disadvantage of the latter recording head, as shown in Japanese Patent Laid-Open No. 5-286131, a recording head is proposed, in which an even piezoelectric material layer is formed across the entire surface of the vibration plate by a deposition technology, the piezoelectric material layer is cut and divided into a shape corresponding to the pressure generating chamber by a lithography method, and the piezoelectric element is formed so as to be independent of another piezoelectric element for each pressure generating chamber.
According to the above-described process, a method for adhering the piezoelectric element on the vibration plate is unnecessary, and there is an advantage that not only the piezoelectric element can be fabricated and installed by accurate and simple means, lithography method, but also the thickness of the piezoelectric element can be made thin and a high-speed drive is enabled.
In such an inkjet printing head, because the pressure generating chamber is formed so as to penetrate in the thickness direction of the head by performing etching from the substrate surface opposite that having the piezoelectric element made thereon or other processing, a pressure generating chamber with a high dimension accuracy can be arranged relatively easily in a high density.
However, in such an ink-jet recording head, in the case where a relatively large substrate having a diameter, for example, of about 6 to 12 inches is used for forming the pressure generating chamber, the thickness of the substrate needs to be made thick due to the problem of handling, and the depth of the pressure generating chamber becomes deeper accompanied with the thickness of the substrate. Therefore, a sufficient rigidity cannot be obtained unless the thickness of compartment walls that divide the pressure generating chambers is made thicker, thus there is a problem that cross talk occurs and a desired ejection characteristic cannot be obtained. In addition, if the compartment wall thickness is made thicker, nozzles cannot be arranged in a high array density, thus there is a problem that a printing quality of high resolution cannot be achieved.
The object of the present invention, in consideration of the foregoing circumstance, is to provide an ink-jet recording head that is capable of improving the rigidity of the compartment wall and of arranging the pressure generating chambers in a high density, and an ink-jet recording apparatus.
A first aspect of the present invention for solving the above-described problem is an ink-jet recording head that comprises a passage-forming substrate comprising at least silicon layer that consists of single crystal silicon and pressure generating chambers defined thereon, which communicate with a nozzle orifice, and a piezoelectric element for generating a pressure change in the pressure generating chamber, the piezoelectric element being provided in a region opposite to the pressure generating chamber via a vibration plate, which constitutes a portion of the pressure generating chamber. The ink-jet recording head is characterized in that it further comprises a joining plate joined to the passage-forming substrate on the surface where the piezoelectric element is formed, and the nozzle orifice is provided on the joining plate.
In the first aspect, the nozzle orifice can be easily formed even if the pressure generating chambers are formed without penetrating the passage-forming substrate. Therefore, the pressure generating chamber can be formed relatively shallowly, and the rigidity of the compartment walls dividing the pressure generating chambers is improved.
A second aspect of the ink-jet recording head of the present invention according to the first aspect is characterized in that an integrated circuit is formed on the joining plate.
In the second aspect, the integrated circuit is formed on the joining plate joined to the passage-forming substrate, thus the manufacturing process of the ink-jet recording head can be simplified and the number of parts can be reduced, leading to reduction in cost.
A third aspect of the ink-jet recording head of the present invention according to the first or second aspect is characterized in that the joining plate is a sealing plate that includes a piezoelectric element holding portion capable of sealing a space in a state where the space is secured for the piezoelectric element such that the movement thereof is not interfered with, in a region opposite to the piezoelectric element.
In the third aspect, a break of the piezoelectric element due to external environment is prevented.
A fourth aspect of the ink-jet recording head of the present invention according to the second or third aspect is characterized in that the integrated circuit is a driving circuit for driving the piezoelectric element.
In the fourth aspect, the driving circuit for driving the piezoelectric element can be formed relatively easily.
A fifth aspect of the ink-jet recording head of the present invention according to the second or third aspect is characterized in that the integrated circuit is a temperature detecting means for detecting a temperature of a head or a temperature control circuit for controlling the temperature.
In the fifth aspect, the temperature detecting means or the temperature control circuit can be formed relatively easily.
A sixth aspect of the ink-jet recording head of the present invention according to the second or third aspect is characterized in that the integrated circuit is an ejection number detecting means for detecting the ejection number of ink droplets that are ejected from the nozzle orifice.
In the sixth aspect, the ejection number detecting means can be formed relatively easily.
A seventh aspect of the ink-jet recording head of the present invention according to the third aspect is characterized in that the integrated circuit is a humidity control circuit for performing control of humidity detecting means for detecting humidity of the piezoelectric element holding portion.
In the seventh aspect, the humidity control circuit can be formed relatively easily.
An eighth aspect of the ink-jet recording head of the present invention according to any one of the second to seventh aspects is characterized in that the integrated circuit is provided on the opposite surface with the joining surface of the joining plate with the passage-forming substrate.
In the eighth aspect, wiring of the integrated circuit can be taken out at the surface of the joining plate.
A ninth aspect of the ink-jet recording head of the present invention according to any one of the second to seventh aspects is characterized in that the integrated circuit is provided on the joining surface of the joining plate with the passage-forming substrate, and the piezoelectric element and the integrated circuit are electrically connected by flip chip mounting.
In the ninth aspect, by joining the passage-forming substrate and the joining plate, the integrated circuit and the piezoelectric element can be directly connected.
A tenth aspect of the ink-jet recording head of the present invention according to the ninth aspect is characterized in that connection wiring is formed to connect the integrated circuit and external wiring, and the integrated circuit and the connection wiring are electrically connected by flip chip mounting.
In the tenth aspect, by joining the passage-forming substrate and the joining plate, the integrated circuit and the connection wiring can be directly connected.
An eleventh aspect of the ink-jet recording head of the present invention according to the ninth aspect or tenth aspect is characterized in that the integrated circuit and the piezoelectric element or the connection wiring are connected by an anisotropic conductive material(e.g. anisotropic conductive film).
In the eleventh aspect, the integrated circuit and the piezoelectric element or the connection wiring can be connected relatively easily and accurately.
A twelfth aspect of the ink-jet recording head of the present invention according to any one of the first to eleventh aspects is characterized in that the joining plate consists of a single crystal silicon substrate.
In the twelfth aspect, the integrated circuit can be formed on the joining plate relatively easily and integrally with good precision.
A thirteenth aspect of the ink-jet recording head of the present invention according to any one of the first to twelfth aspects is characterized in that the pressure generating chamber is formed on one surface of the passage-forming substrate without penetrating the passage-forming substrate, and a reservoir for supplying ink to the pressure generating chamber is formed on the other surface of the passage-forming substrate.
In the thirteenth aspect, the pressure generating chamber can be formed relatively shallowly, and the rigidity of the compartment wall dividing the pressure generating chambers is improved. Moreover, a reservoir with a sufficiently large volume relative to that of the pressure generating chamber is provided, and changes in inner pressure are absorbed by ink itself in the reservoir.
A fourteenth aspect of the ink-jet recording head of the present invention according to the thirteenth aspect is characterized in that the reservoir directly communicates with the pressure generating chamber.
In the fourteenth aspect, ink is directly supplied from the reservoir to each pressure generating chamber.
A fifteenth aspect of the ink-jet recording head of the present invention according to the thirteenth aspect is characterized in that an ink communicating path communicating with one end portion in the longitudinal direction of the pressure generating chamber is formed on one surface of the passage-forming substrate, and the reservoir communicates with the ink communicating path.
In the fifteenth aspect, because ink is supplied from the reservoir to each pressure generating chamber through the ink communicating path, ink resistance can be controlled at a narrowed portion in spite of variation of a sectional area of a communicating portion between the reservoir and the ink communicating path, thus variation of ink ejection characteristic among the pressure generating chambers can be reduced.
A sixteenth aspect of the ink-jet recording head of the present invention according to the fifteenth aspect is characterized in that an ink communicating path is provided for each pressure generating chamber.
In the sixteenth aspect, ink is supplied from the reservoir to each pressure generating chamber through the ink communicating path provided for each pressure generating chamber.
A seventeenth aspect of the ink-jet recording head of the present invention according to the fifteenth aspect is characterized in that the ink communicating path is continuously provided across the direction where the pressure generating chambers are parallelly provided.
In the seventeenth aspect, ink is supplied from the reservoir to each pressure generating chamber through a common ink communicating path.
An eighteenth aspect of the ink-jet recording head of the present invention according to any one of the thirteenth to seventeenth aspects is characterized in that a nozzle communicating path communicating the pressure generating chamber with the nozzle orifice is provided at the end portion opposite to the reservoir in the longitudinal direction of the pressure generating chamber.
In the eighteenth aspect, ink is stably supplied from the reservoir to the pressure generating chamber, and ink is excellently ejected from the nozzle orifice.
A nineteenth aspect of the ink-jet recording head of the present invention according to the eighteenth aspect is characterized in that the nozzle communicating path is formed by removing the vibration plate.
In the nineteenth aspect, the nozzle communicating path can be easily formed.
A twentieth aspect of the ink-jet recording head of the present invention according to the eighteenth or nineteenth aspect is characterized in that the inner surface of the nozzle communicating path is covered with an adhesive agent.
In the twentieth aspect, peeling off of the vibration plate due to ink flow through the nozzle communicating path is prevented.
A twenty-first aspect of the ink-jet recording head of the present invention according to any one of the first to twentieth aspects is characterized in that the passage-forming substrate consists only of a silicon layer.
In the twenty-first aspect, the pressure generating chamber is defined only by the silicon layer.
A twenty-second aspect of the ink-jet recording head of the present invention according to any one of the first to twentieth aspects is characterized in that the passage-forming substrate consists of an SOI substrate having silicon layers on both surfaces of an insulation layer.
In the twenty-second aspect, patterning for the pressure generating chamber, the reservoir, or the like can be performed relatively easily with good precision.
A twenty-third aspect of the ink-jet recording head of the present invention according to any one of the first to twentieth aspects is characterized in that the passage-forming substrate consists of a substrate having at least silicon layers on both surfaces of a boron doped silicon layer.
In the twenty-third aspect, patterning for the pressure generating chamber, reservoir, or the like can be performed relatively easily with good precision.
A twenty-fourth aspect of the ink-jet recording head of the present invention according to any one of the first to twenty-third aspects is characterized in that the plane orientation of the silicon layer that consists of the passage-forming substrate is a (100) plane.
In the twenty-fourth aspect, the reservoir or the like can be formed with high precision also by wet etching.
A twenty-fifth aspect of the ink-jet recording head of the present invention according to the twenty-fourth aspect is characterized in that the lateral cross-sectional surface of the pressure generating chamber has an approximately triangular shape.
In the twenty-fifth aspect, because the rigidity of the compartment wall between the pressure generating chambers is significantly improved, the pressure generating chambers can be arranged in a high density, and cross talk can be prevented.
A twenty-sixth aspect of the ink-jet recording head of the present invention according to any one of the first to twenty-fifth aspects is characterized in that the pressure generating chamber is formed by anisotropic etching, and each layer that constitutes the vibration plate and the piezoelectric element is formed by a deposition and lithography method.
In the twenty-sixth aspect, the ink-jet recording head having the nozzle orifices in a high density can be manufactured relatively easily in a large amount.
A twenty-seventh aspect of the present invention is characterized in that the ink-jet recording apparatus comprises the ink-jet recording head according to any one of the first to twenty-sixth aspects.
In the twenty-seventh aspect, the ink-jet recording apparatus having an improved ink ejection characteristic of the head and a high density thereof can be realized.